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Title: THE DECAYING LONG-PERIOD OSCILLATION OF A STELLAR MEGAFLARE

We analyze and interpret the oscillatory signal in the decay phase of the U-band light curve of a stellar megaflare observed on 2009 January 16 on the dM4.5e star YZ CMi. The oscillation is well approximated by an exponentially decaying harmonic function. The period of the oscillation is found to be 32 minutes, the decay time about 46 minutes, and the relative amplitude 15%. As this observational signature is typical of the longitudinal oscillations observed in solar flares at extreme ultraviolet and radio wavelengths, associated with standing slow magnetoacoustic waves, we suggest that this megaflare may be of a similar nature. In this scenario, macroscopic variations of the plasma parameters in the oscillations modulate the ejection of non-thermal electrons. The phase speed of the longitudinal (slow magnetoacoustic) waves in the flaring loop or arcade, the tube speed, of about 230 km s{sup -1} would require a loop length of about 200 Mm. Other mechanisms, such as standing kink oscillations, are also considered.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. Institute of Solar Terrestrial Physics, Irkutsk (Russian Federation)
  2. Centre for Fusion, Space and Astrophysics, Physics Department, University of Warwick, Coventry CV4 7AL (United Kingdom)
  3. Astrophysics Research Centre, School of Mathematics and Physics, Queen's University, Belfast BT7 1NN (United Kingdom)
  4. Centre for Mathematical Plasma Astrophysics, Department of Mathematics, KU Leuven, Celestijnenlaan 200B bus 2400, B-3001 Leuven (Belgium)
  5. NASA Goddard Space Flight Center, Code 671, Greenbelt, MD 20771 (United States)
Publication Date:
OSTI Identifier:
22130977
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 773; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; AMPLITUDES; DECAY; ELECTRONS; EXTREME ULTRAVIOLET RADIATION; MAGNETOACOUSTIC WAVES; OSCILLATIONS; PLASMA; SOLAR FLARES; VARIATIONS; VELOCITY; VISIBLE RADIATION